Mask filter



FIG. 1 is a front elevation view of a mask filter;

FIG. 2 is a rear elevation view thereof;

FIG. 3 is a top plan view thereof;

FIG. 4 is a bottom plan view thereof;

FIG. 5 is a right side elevation view thereof;

FIG. 6 is a left side elevation view thereof;

FIG. 7 is a top, front, right perspective view thereof;

FIG. 8 is a right side elevation view of the mask filter of FIG. 1 , shown in a folded configuration for clarity of disclosure;

FIG. 9 is an enlarged detail view of the portion of FIG. 8 taken along line 9′-9, shown in perspective; and,

FIG. 10 is a top, front, right perspective view of the mask filter in condition of use.

In the drawings, the dotted lines depict unclaimed portions of the mask filter and form no part of the claimed design. The dash-dot-dash broken lines define the boundaries of the claim. The equal-length broken lines in FIG. 10 , showing a human head and shoulders, depict environmental structure only and form no part of the claimed design. All broken and dotted lines form no part of the claim. 

CLAIM The ornamental design for a mask filter, as shown and described. 